- any of several venomous Old World snakes of the genus Vipera, especially V. berus, a small snake common in northern Eurasia.
- any related snakes belonging to the family Viperidae, characterized by erectile, venom-conducting fangs.
- pit viper.
- any of various venomous or supposedly venomous snakes.
- a malignant or spiteful person.
- a false or treacherous person.
- (initial capital letter) Military. a 9-pound (4 kg), shoulder-launched, unguided U.S. Army antitank rocket with an effective range of 273 yards (250 meters).
- to nourish a viper in one’s bosom, to befriend a person who proves to be treacherous.
- any venomous Old World snake of the family Viperidae, esp any of the genus Vipera (the adder and related forms), having hollow fangs in the upper jaw that are used to inject venom
- any of various other snakes, such as the horned viper
- See pit viper
- a malicious or treacherous person
1520s, from Middle French vipere, from Latin vipera “viper, snake, serpent,” from vivus “alive, living” (see vital) + parere “bring forth, bear” (see pare). It formerly was believed (mistakenly) that the viper does not lay eggs. Applied to persons of spiteful character since at least 1590s. The only venomous snake found in Great Britain. Replaced native adder. “The flesh of the viper was formerly regarded as possessing great nutritive or restorative properties, and was frequently used medicinally” [OED]; hence viper wine, wine medicated with some kind of extract from vipers, used 17c. by “gray-bearded gallants” in a bid “to feele new lust, and youthfull flames agin.”